Runflat tire with thermoplastic sidewall insert

ABSTRACT

The invention is directed to a pneumatic runflat tire comprising a sidewall insert, the sidewall insert comprising an axially layered thermoplastic.

BACKGROUND OF THE INVENTION

The desire for improved fuel efficiency in automobiles, trucks, aircraftand the like has led to the need for more fuel efficient tires. One wayin which tires can be more fuel efficient is through reduced weight ofthe tires. It is therefore desirable to reduce the weight of tires whilemaintaining the physical properties and performance of the various tirecomponents.

SUMMARY OF THE INVENTION

The present invention is directed to a pneumatic runflat tire comprisinga sidewall insert, the sidewall insert comprising an axially layeredthermoplastic.

The invention is further directed to a method of making a pneumaticrunflat tire, comprising the steps of

applying one or more tire components to a tire building machine; and

applying a plurality of layers of a thermoplastic to the one or morecomponents to form an axially-layered thermoplastic runflat insert.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary cross-sectional view of a tire showing its treadand carcass with one ply and one insert axially inward of the ply in thesidewall region of the tire as an embodiment of the invention.

FIG. 2 is schematic representation of a method of making a runflat tireaccording to the present invention.

FIG. 3 is cross section of a partially built runflat insert.

DETAILED DESCRIPTION OF THE INVENTION

There is disclosed a pneumatic runflat tire comprising a sidewallinsert, the sidewall insert comprising an axially layered thermoplastic.

There is further disclosed a method of making a pneumatic runflat tire,comprising the steps of

applying one or more tire components to a tire building machine; and

applying a plurality of layers of a thermoplastic to the one or morecomponents to form an axially-layered thermoplastic runflat insert.

Tires containing the thermoplastic runflat inserts of this invention canbe comprised of a toroidally-shaped carcass and an outer,circumferential tread designed to be ground-contacting, wherein saidcarcass is comprised of two spaced-apart inextensible bead portions, twospaced-apart sidewalls each individually extending radially inward fromand connecting said tread to said bead potions and at least one cordreinforced ply extending from bead to bead and through the sidewalls; animprovement in which a substantially crescent-shaped rubber insert isjuxtapositioned to and axially inward of at least one of said carcassplies in each of said sidewalls of the tire.

So constructed, the runflat tire with a thermoplastic insert is lighterthan prior art runflat tires with conventional inserts made ofcompounded rubber. Such rubber inserts have a high carbon black contentto ensure a sufficient stiffness to support a tire during a deflationepisode. By contrast, a runflat tire with a thermoplastic insert hassufficient stiffness, but at lower overall tire weight.

Preferably, the insert has a maximum thickness at a location aboutmidway between the bead portions and the tread in the sidewall region ofthe tire.

In the practice of this invention, a significant function of the insertin the sidewall portion of the tire is to stiffen/support the sidewallstructure when the tire is operated without inflation pressure.

The shape of the insert is described as being substantially crescent inshape. This is intended to also include an entrunkated crescent shape,particularly where the entrunkated portion of the crescent-shaped insertis juxtapositioned to the tire's bead portion.

In further practice of the invention, said tire carcass may have fromone to three plies comprised of a first axially inner ply and optionallyone or two additional plies as a second ply and third ply, respectively;each additional ply positioned sequentially axially outward from saidfirst ply in the sidewall region of the tire.

Accordingly, in accordance with this invention, said tire contains oneply in its carcass wherein said insert is juxtapositioned to and axiallyinward of said ply in the sidewall region of the tire.

In further accordance with this invention, said tire contains, in itscarcass, an axially inner first ply and a second ply axially outwardfrom the first ply; wherein said insert is juxtapositioned to andaxially inward of said first ply, in the sidewall region of the tire.

In additional accordance with this invention, said tire contains, in itscarcass, an axially inner first ply and an axially outer second ply;wherein said insert is juxtapositioned to and interposed between saidfirst and second ply, in the sidewall region of the tire.

In further accordance with this invention, said tire contains, in itscarcass, an axially inner first ply and an axially outer second ply;wherein one of said inserts is juxtapositioned to and interposed betweensaid first and second ply, in the sidewall region of the tire, andanother of said inserts is juxtapositioned to and axially inward of saidfirst ply, in the sidewall region of the tire.

In further accordance with this invention, said tire contains, in itscarcass, an axially inner first ply, a second ply axially outward fromsaid first ply and a third ply axially outward from said second ply;wherein said insert is juxtapositioned to and axially inward of saidfirst ply, in the sidewall region of the tire.

In additional accordance with this invention, said tire contains, in itscarcass, an axially inner first ply, a second ply axially outward fromsaid first ply and a third ply axially outward from said second ply;wherein said insert is juxtapositioned to and interposed between (a)said first and second plies and/or (b) said second and third plies, inthe sidewall region of the tire.

In further accordance with this invention, said tire contains, in itscarcass, an axially inner first ply, a second ply axially outward fromsaid first ply and a third ply axially outward from said second ply;wherein said insert is juxtapositioned to and interposed between (a)said first and second plies and/or (b) said second and third plies, inthe sidewall region of the tire and, also, an insert juxtapositioned toand axially inward of the innermost of said plies.

In one embodiment, the innermost ply, or plies, has synthetic or textilecord reinforcement of polyester, nylon, rayon or aramid, preferablynylon; while the outermost ply preferably has aramid, rayon, carbonfiber, fiberglass or metal cord reinforcement, preferably brass and/orzinc-coated steel cords.

Thus, in a preferred embodiment, the first ply has reinforcing cords ofrayon and the second and additional plies are cords of rayon.

In one aspect, the outermost ply preferably has cords of a highermodulus (i.e., steel cords) and the innermost ply, or plies, have cordsof a lower modulus (i.e., nylon or rayon).

At least one ply, preferably the innermost ply, extended from bead coreto bead cord and wraps around the bead core. Alternatively, where two ormore plies are used, at least one of the additional plies, whileextending from bead core to bead core, does not actually wrap around thebead core.

Referring to the drawings, FIG. 1 shows the fragmentary cross-section ofa runflat tire 1, its tread 2, bead portion 3, sidewall or sidewallregion 4, inextensible wire bead core 5, rubber chafer 6, rubbertoeguard 7, rubber composition innerliner 8, belt structure 9 underlyinga portion of the tread 2, carcass ply 10, carcass ply turnup 11,thermoplastic insert 12 and apex 13. Thermoplastic insert 12 comprisesaxially-layered thermoplastic layers 22, as will be discussed in moredetail. A similar construction is used on the section of the tireopposite the radial centerline of the tire (not shown).

The cords for use in the carcass plies may comprise from one(monofilament) to multiple twisted filaments. The number of totalfilaments in the cord may range from 1 to 13. The cords, particularlymetallic cords, of the carcass ply are generally oriented such that thetire according to the present invention is what is commonly referred toas a radial.

The cords of the carcass ply intersect the equatorial plane (EP) of thetire at an angle in the range of from 75° to 105°. Preferably, the cordsintersect at an angle of from 82° to 98°. A more preferred range is from89° to 91°.

The first and second reinforcing ply structure each may comprise asingle ply layer; however, any number of carcass plies may be used. Asfurther illustrated in FIG. 1, the first ply structure has a pair ofturnup ends respectively which wrap about each bead core 5 of the beadportion 3 of the carcass. The ends 11 of ply 10 are in proximity to thebead core 5 and terminate radially adjacent on either side of the beadcore 5, above the bead core 5 or can be wrapped around the bead core 5and terminates radially below the turnup end 11 of ply 10 as shown. Theturnup ends 11 of ply 10 wrap about the second ply ends and the beadcore 5. The turnup ends of the first ply 11 terminates radially adistance above the nominal rim diameter of the tire 1 in proximity tothe radial location of the maximum section width of the tire. In apreferred embodiment, the turnup ends are located within 20 percent ofthe section height of the tire from the radial location of the maximumsection width, most preferably terminating at the radial location of themaximum section width.

The bead core 5 is preferably constructed of a single or monofilamentsteel wire continuously wrapped. Located within the bead region 3 andthe radially inner portions of the sidewall portions 4 are high moduluselastomeric apex inserts disposed between ply 10 and the turnup ends 11,respectively. The apex 13 extends from the radially outer portion ofbead portions respectively, up into the sidewall portion graduallydecreasing in cross-sectional width. The apex 13 terminates at aradially outer end.

The insert 12 may extend from each bead region radially to the edge ofthe tread, usually to just beneath the reinforcing belt structures 9. Asillustrated in FIG. 1, the sidewall portions include a thermoplasticinsert 12. Additional inserts (not shown) may be included betweenadditional plies (not shown).

In one embodiment, the inserts 12 each have a thickness at its maximumthickness of at least three percent of the maximum section height “SR”at a location approximately radially aligned to the maximum sectionwidth of the tire.

The overall cross-sectional thickness of the combination of elastomericinserts preceding from the bead portions to the radial location of themaximum section width (SW) is preferably of constant thickness. Theoverall sidewall and carcass thickness is at least 0.45 inches (11.5 mm)at the maximum section width location and increases to an overallthickness in the region where it merges into the shoulder near thelateral tread edges. Preferably, the overall thickness of the sidewallin the shoulder region of the tire is at least one hundred percent(100%) of the overall sidewall thickness at the maximum section width(SW). This ratio means that the sidewall can be made substantiallythinner than the predecessor-type runflat tires.

As previously discussed, the tire of the present invention has at leastone ply having a turnup end 11 (wrapped around the bead core 5) whileanother ply can simply be terminated adjacent to the bead core 5 withoutactually wrapping around the bead core 5.

The insert 12 is made of thermoplastic material. The insert 12 isdesigned to prevent the tire's sidewall from collapsing when operatingunder no inflation pressure. The material shape and cross-sectionalprofile is modified to insure the ride performance and sidewall springrate is acceptable. The cross-sectional area of the insert can bereduced without compromising performance characteristics by utilizingstiffer materials in the insert. Thus, weight can be reduced by usingstiffer thermoplastic materials in the insert.

The second insert and third insert, if used, can be of the same ordifferent material physical properties relative to the first insert 12.This means that the combination of a hard second insert, and/or thirdinsert, if used, with a softer first insert 12 is contemplated as wellas the combination of a hard first insert 12 with a softer second and/orthird insert.

The second insert and third insert, if used, are made of thermoplasticor elastomeric material. These inserts can be used in multiples ofinserts interposed between adjacent plies when more than two plies areused in the carcass structure.

The second and third inserts, when used, act as a spacer between theadjacent plies. The cords of the plies particularly the radially outerply is placed in tension when the tire is operated uninflated.

In practice, the compositions for the inserts utilized in this inventionfor the aforesaid pneumatic tire construction are preferablycharacterized by physical properties which enhance their utilization inthe invention which are, collectively, believed to be a departure fromproperties of conventional rubber compositions normally used inpneumatic tire sidewalls, particularly the combination of inserts 12 andwith plies 10 having a combination of either dissimilar or similar highstiffness yet essentially low hysteresis properties.

In particular, for the purposes of this invention, the aforesaid inserts12 are designed to have a high degree of stiffness yet also having lowerweight than for an inserts not containing the thermoplastic.

The thermoplastic inserts are constructed from multiple, relatively thinlayers of thermoplastic material. In one embodiment, the thermoplasticlayers have a thickness in a range of 0.1 to 1 mm (4 to 40 mils). Themultiple layers of thermoplastic are layered sequentially in such a wayas to form the desired cross-sectional thicknesses and shape suitablefor used as a runflat insert. The multiple layers of thermoplastic maybe layered using manual or automatic (continuous) methods.

In one embodiment, the thermoplastic insert is constructed using amethod as illustrated in FIG. 2. In FIG. 2, innerliner material 26(corresponding to the innerliner 8 in FIG. 1) has been built onto tiredrum 30. Thermoplastic material in the form of a continuous tape 22 istransferred onto surface 28 of innerliner material 26 by unwinding fromspool 20 in the direction of arrow 32. Tape 22 is layered to formpartially built insert 24 by sequential application of tape 22 duringrotation of tire drum 30 and spool 20. Insert regions 36A,B areindicated by the areas between the dashed lines 37A and 37B,respectively. Tape 22 is disposed in regions 36A,B of surface 28;regions 36 correspond to the desired location of the inserts 12 (FIG.1).

A partially built insert 24 is shown in cross-section in FIG. 3, with aplurality of layers of tape 22 disposed on surface 28 of innerlinermaterial 26 after sequential rotations of tire drum 30. As is evidentfrom FIG. 3, the various layers of tape 22 are stacked and overlapped insuch a manner as to form the desired cross-sectional thicknesses andshape of the partially built insert 24. The relative overlap ofsequential layers of tape 22 may be controlled by indexing spool 20along its axle 34.

Upon completion of the desired shaped of partially built insert 24, tape22 is cut from spool 20. The remaining tire components (sidewall, beads,tread, etc., not shown) are built onto the tire building drum 30 in theconventional manner. Upon removal of the built green tire from the tiredrum 30 and formation into the conventional toroidal conformation asdepicted in partial cross-section in FIG. 1, the layers of tape 22 areseen to be axially-layered with respect to the axial direction of thetire 1. The layers of tape 22 are fused by application of heat duringcure of tire 1 to form insert 12, or by action of an adhesive applied totape 22.

The construction of insert 12 from thermoplastic tape layers 22facilitates use of a thermoplastic insert in a runflat tire.Construction of a thermoplastic insert from a monolithic, preshapedthermoplastic insert material is difficult due to the high modulus ofthe material. Bending such a monolithic material for use during tirebuilding requires thermal softening of the thermoplastic, which adds alevel of complexity in processing and operator handling due to the hightemperature. With the present method, the relatively thin tape 22 allowseasy handling and application of the thermoplastic during tire buildingwithout need for thermal softening.

The insert 12 comprises a plurality of axially layered thermoplasticlayers. In one embodiment, the insert comprises at least 10 axiallylayered thermoplastic layers.

Suitable thermoplastic materials for use as the tape 22 and insert 12include polyolefin such as polyethylene and polypropylene; polyamidessuch as nylon 6, nylon 6,6; nylon 6,12; polyesters such as polyethyleneterephthalate (PET) and polybutylene terephthalate (PBT); polyphenyleneether (PPE); polyphthalamide (PPA); and the like. Suitablethermoplastics will have a melting temperature greater than thetemperatures experienced during a runflat event by the tire. In oneembodiment, the thermoplastic has a melting temperature greater than160° C. In one embodiment, the thermoplastic has a melting temperaturegreater than 130° C.

The thermoplastic material may be treated on its surface with anadhesive to promote adhesion between the layers of tape 22 and theadhesion between the tape 22 and adjacent rubber components of the tire.In one embodiment, the tape 22 is dipped in an RFL(resorcinol-formaldehyde-latex) type adhesive as is known in the rubbercompounding art. In one embodiment, the tape 22 is dipped in anepoxy-based adhesive. In one embodiment, the tape 22 is dipped in acombination of RFL and epoxy-based adhesives. The adhesive, if used, isthen disposed between the layers of tape 22 in the insert 12.

The tire components other than the thermoplastic insert, such as tread,sidewalls, etc., may be made from rubber compositions with rubbers orelastomers containing olefinic unsaturation. The phrase “rubber orelastomer containing olefinic unsaturation” is intended to include bothnatural rubber and its various raw and reclaim forms as well as varioussynthetic rubbers. In the description of this invention, the terms“rubber” and “elastomer” may be used interchangeably, unless otherwiseprescribed. The terms “rubber composition,” “compounded rubber” and“rubber compound” are used interchangeably to refer to rubber which hasbeen blended or mixed with various ingredients and materials and suchterms are well known to those having skill in the rubber mixing orrubber compounding art. Representative synthetic polymers are thehomopolymerization products of butadiene and its homologues andderivatives, for example, methylbutadiene, dimethylbutadiene andpentadiene as well as copolymers such as those formed from butadiene orits homologues or derivatives with other unsaturated monomers. Among thelatter are acetylenes, for example, vinyl acetylene; olefins, forexample, isobutylene, which copolymerizes with isoprene to form butylrubber; vinyl compounds, for example, acrylic acid, acrylonitrile (whichpolymerize with butadiene to form NBR), methacrylic acid and styrene,the latter compound polymerizing with butadiene to form SBR, as well asvinyl esters and various unsaturated aldehydes, ketones and ethers,e.g., acrolein, methyl isopropenyl ketone and vinylethyl ether. Specificexamples of synthetic rubbers include neoprene (polychloroprene),polybutadiene (including cis-1,4-polybutadiene), polyisoprene (includingcis-1,4-polyisoprene), butyl rubber, halobutyl rubber such aschlorobutyl rubber or bromobutyl rubber, styrene/isoprene/butadienerubber, copolymers of 1,3-butadiene or isoprene with monomers such asstyrene, acrylonitrile and methyl methacrylate, as well asethylene/propylene terpolymers, also known as ethylene/propylene/dienemonomer (EPDM), and in particular, ethylene/propylene/dicyclopentadieneterpolymers. Additional examples of rubbers which may be used includealkoxy-silyl end functionalized solution polymerized polymers (SBR, PBR,IBR and SIBR), silicon-coupled and tin-coupled star-branched polymers.The preferred rubber or elastomers are polybutadiene and SBR.

In one aspect the rubber is preferably of at least two of diene basedrubbers. For example, a combination of two or more rubbers is preferredsuch as cis 1,4-polyisoprene rubber (natural or synthetic, althoughnatural is preferred), 3,4-polyisoprene rubber,styrene/isoprene/butadiene rubber, emulsion and solution polymerizationderived styrene/butadiene rubbers, cis 1,4-polybutadiene rubbers andemulsion polymerization prepared butadiene/acrylonitrile copolymers.

In one aspect of this invention, an emulsion polymerization derivedstyrene/butadiene (E-SBR) might be used having a relatively conventionalstyrene content of about 20 to about 28 percent bound styrene or, forsome applications, an E-SBR having a medium to relatively high boundstyrene content, namely, a bound styrene content of about 30 to about 45percent.

By emulsion polymerization prepared E-SBR, it is meant that styrene and1,3-butadiene are copolymerized as an aqueous emulsion. Such are wellknown to those skilled in such art. The bound styrene content can vary,for example, from about 5 to about 50 percent. In one aspect, the E-SBRmay also contain acrylonitrile to form a terpolymer rubber, as E-SBAR,in amounts, for example, of about 2 to about 30 weight percent boundacrylonitrile in the terpolymer.

Emulsion polymerization prepared styrene/butadiene/acrylonitrilecopolymer rubbers containing about 2 to about 40 weight percent boundacrylonitrile in the copolymer are also contemplated as diene basedrubbers for use in this invention.

The solution polymerization prepared SBR (S-SBR) typically has a boundstyrene content in a range of about 5 to about 50, preferably about 9 toabout 36, percent. The S-SBR can be conveniently prepared, for example,by organo lithium catalyzation in the presence of an organic hydrocarbonsolvent.

In one embodiment, cis 1,4-polybutadiene rubber (BR) may be used. SuchBR can be prepared, for example, by organic solution polymerization of1,3-butadiene. The BR may be conveniently characterized, for example, byhaving at least a 90 percent cis 1,4-content.

The cis 1,4-polyisoprene and cis 1,4-polyisoprene natural rubber arewell known to those having skill in the rubber art.

The term “phr” as used herein, and according to conventional practice,refers to “parts by weight of a respective material per 100 parts byweight of rubber, or elastomer.”

The rubber composition may also include up to 70 phr of processing oil.Processing oil may be included in the rubber composition as extendingoil typically used to extend elastomers. Processing oil may also beincluded in the rubber composition by addition of the oil directlyduring rubber compounding. The processing oil used may include bothextending oil present in the elastomers, and process oil added duringcompounding. Suitable process oils include various oils as are known inthe art, including aromatic, paraffinic, napthenic, vegetable oils, andlow PCA oils, such as MES, TDAE, SRAE and heavy naphthenic oils.

Suitable low PCA oils include those having a polycyclic aromatic contentof less than 3 percent by weight as determined by the IP346 method.Procedures for the IP346 method may be found in Standard Methods forAnalysis & Testing of Petroleum and Related Products and BritishStandard 2000 Parts, 2003, 62nd edition, published by the Institute ofPetroleum, United Kingdom.

The phrase “rubber or elastomer containing olefinic unsaturation” isintended to include both natural rubber and its various raw and reclaimforms as well as various synthetic rubbers. In the description of thisinvention, the terms “rubber” and “elastomer” may be usedinterchangeably, unless otherwise prescribed. The terms “rubbercomposition,” “compounded rubber” and “rubber compound” are usedinterchangeably to refer to rubber which has been blended or mixed withvarious ingredients and materials, and such terms are well known tothose having skill in the rubber mixing or rubber compounding art.

The vulcanizable rubber composition may include from about 10 to about150 phr of silica.

The commonly employed siliceous pigments which may be used in the rubbercompound include conventional pyrogenic and precipitated siliceouspigments (silica). In one embodiment, precipitated silica is used. Theconventional siliceous pigments employed in this invention areprecipitated silicas such as, for example, those obtained by theacidification of a soluble silicate, e.g., sodium silicate.

Such conventional silicas might be characterized, for example, by havinga BET surface area, as measured using nitrogen gas. In one embodiment,the BET surface area may be in the range of about 40 to about 600 squaremeters per gram. In another embodiment, the BET surface area may be in arange of about 80 to about 300 square meters per gram. The BET method ofmeasuring surface area is described in the Journal of the AmericanChemical Society, Volume 60, Page 304 (1930).

The conventional silica may also be characterized by having adibutylphthalate (DBP) absorption value in a range of about 100 to about400, alternatively about 150 to about 300.

The conventional silica might be expected to have an average ultimateparticle size, for example, in the range of 0.01 to 0.05 micron asdetermined by the electron microscope, although the silica particles maybe even smaller, or possibly larger, in size.

Various commercially available silicas may be used, such as, only forexample herein, and without limitation, silicas commercially availablefrom PPG Industries under the Hi-Sil trademark with designations 210,243, etc.; silicas available from Rhodia, with, for example,designations of Z1165MP and Z165GR and silicas available from Degussa AGwith, for example, designations VN2 and VN3, etc.

The vulcanizable rubber composition may include from 1 to 100 phr ofcarbon black, crosslinked particulate polymer gel, ultra high molecularweight polyethylene (UHMWPE) or plasticized starch.

Commonly employed carbon blacks can be used as a conventional filler.Representative examples of such carbon blacks include N110, N121, N134,N220, N231, N234, N242, N293, N299, N315, N326, N330, N332, N339, N343,N347, N351, N358, N375, N539, N550, N582, N630, N642, N650, N683, N754,N762, N765, N774, N787, N907, N908, N990 and N991. These carbon blackshave iodine absorptions ranging from 9 to 145 g/kg and DBP numberranging from 34 to 150 cm³/100 g.

Other fillers may be used in the rubber composition including, but notlimited to, particulate fillers including ultra high molecular weightpolyethylene (UHMWPE), particulate polymer gels including but notlimited to those disclosed in U.S. Pat. Nos. 6,242,534; 6,207,757;6,133,364; 6,372,857; 5,395,891; or 6,127,488, and plasticized starchcomposite filler including but not limited to that disclosed in U.S.Pat. No. 5,672,639.

In one embodiment the rubber composition for use in the tire tread maycontain a conventional sulfur containing organosilicon compound.Examples of suitable sulfur containing organosilicon compounds are ofthe formula:

Z-Alk-S_(n)-Alk-Z   II

in which Z is selected from the group consisting of

where R¹ is an alkyl group of 1 to 4 carbon atoms, cyclohexyl or phenyl;R² is alkoxy of 1 to 8 carbon atoms, or cycloalkoxy of 5 to 8 carbonatoms; Alk is a divalent hydrocarbon of 1 to 18 carbon atoms and n is aninteger of 2 to 8.

Specific examples of sulfur containing organosilicon compounds which maybe used in accordance with the present invention include:3,3′-bis(trimethoxysilylpropyl)disulfide,3,3′-bis(triethoxysilylpropyl)disulfide,3,3′-bis(triethoxysilylpropyl)tetrasulfide,3,3′-bis(triethoxysilylpropyl)octasulfide,3,3′-bis(trimethoxysilylpropyl)tetrasulfide,2,2′-bis(triethoxysilylethyl)tetrasulfide,3,3′-bis(trimethoxysilylpropyl)trisulfide,3,3′-bis(triethoxysilylpropyl)trisulfide,3,3′-bis(tributoxysilylpropyl)disulfide,3,3′-bis(trimethoxysilylpropyl)hexasulfide,3,3′-bis(trimethoxysilylpropyl)octasulfide,3,3′-bis(trioctoxysilylpropyl)tetrasulfide,3,3′-bis(trihexoxysilylpropyl)disulfide,3,3′-bis(tri-2″-ethylhexoxysilylpropyl)trisulfide,3,3′-bis(triisooctoxysilylpropyl)tetrasulfide,3,3′-bis(tri-t-butoxysilylpropyl)disulfide, 2,2′-bis(methoxy diethoxysilyl ethyl)tetrasulfide, 2,2′-bis(tripropoxysilylethyl)pentasulfide,3,3′-bis(tricyclonexoxysilylpropyl)tetrasulfide,3,3′-bis(tricyclopentoxysilylpropyl)trisulfide,2,2′-bis(tri-2″-methylcyclohexoxysilylethyl)tetrasulfide,bis(trimethoxysilylmethyl)tetrasulfide, 3-methoxy ethoxy propoxysilyl3′-diethoxybutoxy-silylpropyltetrasulfide, 2,2′-bis(dimethylmethoxysilylethyl)disulfide, 2,2′-bis(dimethylsec.butoxysilylethyl)trisulfide, 3,3′-bis(methylbutylethoxysilylpropyl)tetrasulfide, 3,3′-bis(dit-butylmethoxysilylpropyl)tetrasulfide, 2,2′-bis(phenyl methylmethoxysilylethyl)trisulfide, 3,3′-bis(diphenylisopropoxysilylpropyl)tetrasulfide, 3,3′-bis(diphenylcyclohexoxysilylpropyl)disulfide, 3,3′-bis(dimethylethylmercaptosilylpropyl)tetrasulfide, 2,2′-bis(methyldimethoxysilylethyl)trisulfide, 2,2′-bis(methylethoxypropoxysilylethyl)tetrasulfide, 3,3′-bis(diethylmethoxysilylpropyl)tetrasulfide, 3,3′-bis(ethyl di-sec.butoxysilylpropyl)disulfide, 3,3′-bis(propyldiethoxysilylpropyl)disulfide, 3,3′-bis(butyldimethoxysilylpropyl)trisulfide, 3,3′-bis(phenyldimethoxysilylpropyl)tetrasulfide, 3-phenyl ethoxybutoxysilyl3′-trimethoxysilylpropyl tetrasulfide,4,4′-bis(trimethoxysilylbutyl)tetrasulfide,6,6′-bis(triethoxysilylhexyl)tetrasulfide,12,12′-bis(triisopropoxysilyldodecyl)disulfide,18,18′-bis(trimethoxysilyloctadecyl)tetrasulfide,18,18′-bis(tripropoxysilyloctadecenyl)tetrasulfide,4,4′-bis(trimethoxysilyl-buten-2-yl)tetrasulfide,4,4′-bis(trimethoxysilylcyclohexylene)tetrasulfide,5,5′-bis(dimethoxymethylsilylpentyl)trisulfide,3,3′-bis(trimethoxysilyl-2-methylpropyl)tetrasulfide,3,3′-bis(dimethoxyphenylsilyl-2-methylpropyl)disulfide.

In one embodiment, the sulfur containing organosilicon compounds are the3,3′-bis(trimethoxy or triethoxy silylpropyl)sulfides. In oneembodiment, the sulfur containing organosilicon compounds are3,3′-bis(triethoxysilylpropyl)disulfide and3,3′-bis(triethoxysilylpropyl)tetrasulfide. Therefore, as to formula II,Z may be

where R² is an alkoxy of 2 to 4 carbon atoms, alternatively 2 carbonatoms; alk is a divalent hydrocarbon of 2 to 4 carbon atoms,alternatively with 3 carbon atoms; and n is an integer of from 2 to 5,alternatively 2 or 4.

In another embodiment, suitable sulfur containing organosiliconcompounds include compounds disclosed in U.S. Pat. No. 6,608,125. Asdisclosed in U.S. Pat. No. 6,608,125, these sulfur containingorganosilicon compounds are of the formula G-C(═O)—S—CH₂CH₂CH₂SiX₃wherein each X is an independently selected RO-group wherein each R isindependently selected from the group consisting of hydrogen, alkyl thatmay or may not contain unsaturation, alkenyl groups, aryl groups, andaralkyl groups, such moieties other than hydrogen having from 1 to 18carbon atoms, and G is a monovalent alkyl of from 6 to 8 carbon atoms.In one embodiment, the sulfur containing organosilicon compoundsincludes 3-(octanoylthio)-1-propyltriethoxysilane,CH₃(CH₂)₆C(═O)—S—CH₂CH₂CH₂Si(OCH₂CH₃)₃, which is available commerciallyas NXT™ from GE Silicones.

In another embodiment, suitable sulfur containing organosiliconcompounds include those disclosed in U.S. Patent Publication2003/0130535. As disclosed in U.S. Patent Publication 2003/0130535,these sulfur containing organosilicon compounds are of the formulas IIIor IV

wherein: R is a methyl or ethyl group;

R′ is identical or different and is a C₉C₃₀ branched or unbranchedmonovalent alkyl or alkenyl group, aryl group, aralkyl group, branchedor unbranched C₂-C₃₀ alkyl ether group, branched or unbranched C₂-C₃₀alkyl polyether group or R′″₃Si, where R′″ is C₁-C₃₀ branched orunbranched alkyl or alkenyl group, aralkyl group or aryl group, R″ is abranched or unbranched, saturated or unsaturated, aliphatic, aromatic ormixed aliphatic/aromatic divalent C₁-C₃₀ hydrocarbon group;

X is SH where n=1 and m=1, S where n=2 and m=1-10 and mixtures thereof,S(C═O)—R′″ where n=1 and m=1 or H where n=1 and m=1;

R″ may mean CH₂, CH₂CH₂, CH₂CH₂CH₂, CH₂CH₂CH₂CH₂, CH(CH₃), CH₂CH(CH₃),C(CH₃)₂, CH(C₂H₅), CH₂CH₂CH(CH₃), CH₂CH(CH₃)CH₂ or

In one embodiment, the sulfur containing organosilicon compound is offormula III, R is ethyl, R′ is C₁₂-C₁₄ alkyl, R″ is CH₂CH₂CH₂, X is SH,n is 1 and m is 1. In one embodiment, the sulfur containingorganosilicon compound is Si-363 from Degussa.

The amount of the sulfur containing organosilicon compound in a rubbercomposition will vary depending on the level of other additives that areused. Generally speaking, the amount of the compound will range from 0.5to 20 phr. In one embodiment, the amount will range from 1 to 10 phr.

It is readily understood by those having skill in the art that therubber composition would be compounded by methods generally known in therubber compounding art, such as mixing the various sulfur-vulcanizableconstituent rubbers with various commonly used additive materials suchas, for example, sulfur donors, curing aids, such as activators andretarders and processing additives, such as oils, resins includingtackifying resins and plasticizers, fillers, pigments, fatty acid, zincoxide, waxes, antioxidants and antiozonants and peptizing agents. Asknown to those skilled in the art, depending on the intended use of thesulfur vulcanizable and sulfur-vulcanized material (rubbers), theadditives mentioned above are selected and commonly used in conventionalamounts. Representative examples of sulfur donors include elementalsulfur (free sulfur), an amine disulfide, polymeric polysulfide andsulfur olefin adducts. In one embodiment, the sulfur-vulcanizing agentis elemental sulfur. The sulfur-vulcanizing agent may be used in anamount ranging from 0.5 to 8 phr, alternatively with a range of from 1.5to 6 phr. Typical amounts of tackifier resins, if used, comprise about0.5 to about 10 phr, usually about 1 to about 5 phr. Typical amounts ofprocessing aids comprise about 1 to about 50 phr. Typical amounts ofantioxidants comprise about 1 to about 5 phr. Representativeantioxidants may be, for example, diphenyl-p-phenylenediamine andothers, such as, for example, those disclosed in The Vanderbilt RubberHandbook (1978), pages 344 through 346. Typical amounts of antiozonantscomprise about 1 to 5 phr. Typical amounts of fatty acids, if used,which can include stearic acid comprise about 0.5 to about 3 phr.Typical amounts of zinc oxide comprise about 2 to about 5 phr. Typicalamounts of waxes comprise about 1 to about 5 phr. Often microcrystallinewaxes are used. Typical amounts of peptizers comprise about 0.1 to about1 phr. Typical peptizers may be, for example, pentachlorothiophenol anddibenzamidodiphenyl disulfide.

Accelerators are used to control the time and/or temperature requiredfor vulcanization and to improve the properties of the vulcanizate. Inone embodiment, a single accelerator system may be used, i.e., primaryaccelerator. The primary accelerator(s) may be used in total amountsranging from about 0.5 to about 4, alternatively about 0.8 to about 1.5,phr. In another embodiment, combinations of a primary and a secondaryaccelerator might be used with the secondary accelerator being used insmaller amounts, such as from about 0.05 to about 3 phr, in order toactivate and to improve the properties of the vulcanizate. Combinationsof these accelerators might be expected to produce a synergistic effecton the final properties and are somewhat better than those produced byuse of either accelerator alone. In addition, delayed actionaccelerators may be used which are not affected by normal processingtemperatures but produce a satisfactory cure at ordinary vulcanizationtemperatures. Vulcanization retarders might also be used. Suitable typesof accelerators that may be used in the present invention are amines,disulfides, guanidines, thioureas, thiazoles, thiurams, sulfenamides,dithiocarbamates and xanthates. In one embodiment, the primaryaccelerator is a sulfenamide. If a second accelerator is used, thesecondary accelerator may be a guanidine, dithiocarbamate or thiuramcompound.

The mixing of the rubber composition can be accomplished by methodsknown to those having skill in the rubber mixing art. For example, theingredients are typically mixed in at least two stages, namely, at leastone non-productive stage followed by a productive mix stage. The finalcuratives including sulfur-vulcanizing agents are typically mixed in thefinal stage which is conventionally called the “productive” mix stage inwhich the mixing typically occurs at a temperature, or ultimatetemperature, lower than the mix temperature(s) than the precedingnon-productive mix stage(s). The terms “non-productive” and “productive”mix stages are well known to those having skill in the rubber mixingart. The rubber composition may be subjected to a thermomechanicalmixing step. The thermomechanical mixing step generally comprises amechanical working in a mixer or extruder for a period of time suitablein order to produce a rubber temperature between 140° C. and 190° C. Theappropriate duration of the thermomechanical working varies as afunction of the operating conditions, and the volume and nature of thecomponents. For example, the thermomechanical working may be from 1 to20 minutes.

The rubber composition may be incorporated in a variety of rubbercomponents of the tire. For example, the rubber component may be a tread(including tread cap and tread base), sidewall, apex, chafer, sidewallinsert, wirecoat or innerliner. In one embodiment, the compound is atread.

The pneumatic tire of the present invention may be a race tire,passenger tire, aircraft tire, agricultural, earthmover, off-the-road,truck tire, and the like. In one embodiment, the tire is a passenger ortruck tire. The tire may also be a radial or bias.

Vulcanization of the pneumatic tire of the present invention isgenerally carried out at conventional temperatures ranging from about100° C. to 200° C. In one embodiment, the vulcanization is conducted attemperatures ranging from about 110° C. to 180° C. Any of the usualvulcanization processes may be used such as heating in a press or mold,heating with superheated steam or hot air. Such tires can be built,shaped, molded and cured by various methods which are known and will bereadily apparent to those having skill in such art.

The runflat tire containing the inserts of this invention can be built,shaped, molded and cured by various methods that will be readilyapparent to those having skill in the art.

While certain representative embodiments and details have been shown forthe purpose of illustrating the invention, it will be apparent to thoseskilled in this art that various changes and modifications may be madetherein without departing from the spirit or scope of the invention.

1. A pneumatic runflat tire comprising a sidewall insert, the sidewallinsert comprising an axially layered thermoplastic.
 2. The pneumaticrunflat tire of claim 1, wherein the thermoplastic is selected from thegroup consisting of polyethylene, polypropylene, polyamide, polyester,polyphenylene ether, and polyphthalamide.
 3. The pneumatic runflat tireof claim 1, wherein the thermoplastic is polyethylene.
 4. The pneumaticrunflat tire of claim 1, wherein the sidewall insert further comprisesan adhesive selected from the group consisting of an RFL adhesive and anepoxy-based adhesive.
 5. The pneumatic runflat tire of claim 1, whereinthe sidewall insert comprises a plurality of thermoplastic layers. 6.The pneumatic runflat tire of claim 1, wherein the sidewall insertcomprises a plurality of thermoplastic layers, wherein the thermoplasticlayers have a layer thickness ranging from 0.1 to 1 mm.
 7. The pneumaticrunflat tire of claim 1, wherein the sidewall insert comprises at least10 axially layered thermoplastic layers.
 8. The pneumatic runflat tireof claim 1, wherein the sidewall insert comprises a plurality ofthermoplastic layers, wherein an adhesive is disposed between thethermoplastic layers.
 9. The pneumatic runflat tire of claim 1, whereinthe sidewall insert comprises at least 10 axially layered thermoplasticlayers, wherein an adhesive is disposed between the thermoplasticlayers.
 10. A method of making a pneumatic runflat tire, comprising thesteps of applying one or more tire components to a tire buildingmachine; and applying a plurality of layers of a thermoplastic to theone or more components to form an axially-layered thermoplastic runflatinsert.
 11. The method of claim 10, wherein the thermoplastic isselected from the group consisting of polyethylene, polypropylene,polyamide, polyester, polyphenylene ether, and polyphthalamide.
 12. Themethod of claim 10, wherein the thermoplastic is polyethylene.
 13. Themethod of claim 1, wherein the sidewall insert further comprises anadhesive selected from the group consisting of an RFL adhesive and anepoxy-based adhesive.
 14. The method of claim 1, wherein the sidewallinsert comprises a plurality of thermoplastic layers.
 15. The method ofclaim 1, wherein the sidewall insert comprises a plurality ofthermoplastic layers, wherein the thermoplastic layers have a layerthickness ranging from 0.1 to 1 mm.
 16. The method of claim 1, whereinthe sidewall insert comprises at least 10 axially layered thermoplasticlayers.
 17. The method of claim 1, wherein the sidewall insert comprisesa plurality of thermoplastic layers, wherein an adhesive is disposedbetween the thermoplastic layers.
 18. The method of claim 1, wherein thesidewall insert comprises at least 10 axially layered thermoplasticlayers, wherein an adhesive is disposed between the thermoplasticlayers.
 19. A pneumatic runflat tire made by the method of claim 10.